UF Membrane Sizing Calculator
Size your ultrafiltration membrane system — calculate required membrane area, number of modules and skids, temperature-corrected flux, and backwash flow. Based on Metcalf & Eddy membrane filtration design principles.
UF Membrane System Parameters
Enter design inputs to size ultrafiltration membrane modules and skids. Based on Metcalf & Eddy membrane filtration design methodology (Ch. 11).
Net product water required
Typical UF: 20–80 LMH
Backwash water as % of gross output
For viscosity (TCF) correction
Integer count per rack or vessel
e.g. GE ZeeWeed ZW500 = 46 m²
How to Use This Calculator
- 1Enter the design flow — this is the net permeate (product water) you need, in m³/hr. Do not include backwash losses; the calculator accounts for those.
- 2Set the design flux in LMH. For UF treating pre-settled or clarified wastewater, 25–50 LMH is typical. For clean surface water, up to 70–80 LMH may be used. Check manufacturer guidelines for your specific membrane module.
- 3Enter the backwash factor (typically 8–12%) and operating temperature. The temperature correction factor (TCF) adjusts flux for water viscosity changes — important for seasonal variation or cold climates.
- 4Set the module area (e.g. 46 m² for GE ZeeWeed ZW500d) and modules per skid. The calculator divides total required area by module area, rounding up to whole modules, then divides by skid capacity.
- 5Click Calculate to see the membrane area, module count, skid count, installed area, actual operating flux, and backwash flow. The bar charts show how required and installed area compare.
What Is Ultrafiltration (UF) Membrane Technology?
Ultrafiltration is a low-pressure membrane separation process that uses semi-permeable hollow-fibre or flat-sheet membranes with pore sizes in the 0.01–0.1 micron range. Water (the permeate) passes through the membrane under a transmembrane pressure of 0.1–0.5 bar, while suspended solids, bacteria, viruses, colloids, and high-molecular-weight organics are retained on the feed side and periodically removed by backwashing.
Unlike conventional sand filtration, UF provides an absolute barrier to particles larger than its nominal pore size. This makes UF the preferred pre-treatment technology ahead of reverse osmosis (RO) systems, because it delivers consistent SDI (Silt Density Index) values — typically SDI < 3 — that protect expensive RO membranes from fouling. UF membranes also achieve 4-log virus removal and 6-log bacterial removal, enabling treated water to meet drinking water standards without additional disinfection in many applications.
Modern UF systems use submerged or pressurised hollow-fibre modules with automated backwashing sequences (every 20–60 minutes) and periodic chemical enhanced backwash (CEB) or clean-in-place (CIP) to maintain flux over the membrane's design life of 7–10 years.
UF Membrane Sizing Methodology (Metcalf & Eddy)
The sizing approach used in this calculator follows the membrane filtration design framework described in Metcalf & Eddy's Wastewater Engineering: Treatment and Resource Recovery (5th edition, Ch. 11). The key steps are:
Step 1 — Temperature Correction Factor (TCF)
TCF = exp(0.0239 × (T – 20)), where T is operating temperature in °C. At 25°C, TCF ≈ 1.126; at 15°C, TCF ≈ 0.888. Flux is multiplied by TCF to give the corrected (actual) flux at the design temperature.
Step 2 — Gross Flow
Gross flow = Net permeate flow ÷ (1 – backwash factor / 100). Backwash water (used to clean membranes) must be produced and is not available as net product, so the membrane system must generate more than the required net output.
Step 3 — Membrane Area
Total area (m²) = Gross flow (L/hr) ÷ Corrected flux (LMH). The gross flow in m³/hr is converted to L/hr (×1000) before dividing by the LMH flux value.
Step 4 — Modules and Skids
Number of modules = ceil(Total area ÷ Module area). Number of skids = ceil(Modules ÷ Modules per skid). The actual installed area (whole modules) slightly exceeds the calculated requirement — the actual operating flux is therefore slightly lower than the design flux, providing a safety margin.
UF Membranes in Indian Water & Wastewater Treatment
Ultrafiltration has seen rapid adoption in India's water and wastewater sector over the past decade, driven by stricter CPCB discharge standards, growing water scarcity, and the AMRUT and Smart Cities programmes that fund advanced treatment plants.
In municipal drinking water, UF plants have been commissioned in Chennai, Hyderabad, Kochi, and Navi Mumbai to treat river and reservoir water to WHO drinking water standards. In the industrial sector, UF is standard pre-treatment ahead of RO in Effluent Treatment Plants (ETPs) and Sewage Treatment Plants (STPs), particularly where water reuse is mandated. Plants using MBBR technology for biological treatment often follow with UF polishing before RO, enabling tertiary quality water recovery of 85–90%.
For industries subject to CPCB's ZLD mandates — textile dyeing, tanneries, distilleries, and pharma — UF is an essential intermediate step that protects downstream RO membranes and ensures consistent product water quality even when influent characteristics fluctuate.
Selecting UF Modules: GE ZeeWeed, DowDuPont, and INGE
The UF membrane market is dominated by a handful of global manufacturers, each offering hollow-fibre modules in pressurised or submerged configurations:
- GE Water / Suez ZeeWeed (ZW500): The ZW500d module provides 46 m² of membrane area per module and is widely used in India. Typical flux: 25–40 LMH for secondary effluent. Suitable for both submerged and pressurised configurations.
- DuPont Water Solutions (IntegraFlux / SFP): Previously DowDuPont, these pressurised outside-in hollow-fibre modules are popular in industrial pre-treatment and drinking water. Module areas range from 37 to 83 m².
- INGE (TORAY Group — dizzer XL): Inside-out hollow-fibre UF modules with Multibore technology for improved structural stability. Available in 33 and 80 m² configurations, suitable for high-turbidity feeds.
- Pall Corporation / Koch Membrane Systems: Used in pharmaceutical and food & beverage applications where FDA-compliant membranes and high purity are required.
When selecting modules for Zero Liquid Discharge (ZLD) pre-treatment, the ability to handle high TSS, variable COD, and fouling organics in the secondary effluent feed is critical. Robust backwash protocols, CEB capability, and chemical resistance to sodium hypochlorite (NaOCl) cleaning are key selection criteria. Always confirm module specifications, design flux, and warranty conditions with the manufacturer before finalising the design.
Frequently Asked Questions
What is ultrafiltration (UF) membrane treatment?
Ultrafiltration is a pressure-driven membrane process that removes suspended solids, bacteria, viruses, colloids, and high-molecular-weight organics using membranes with 0.01–0.1 micron pore sizes. It operates at low transmembrane pressures (0.1–0.5 bar) and provides an absolute particulate barrier, making it ideal for drinking water treatment, tertiary effluent polishing, and RO pre-treatment.
What is design flux and what values are typical for UF membranes?
Design flux is the permeate flow per unit membrane area per unit time, expressed in LMH (L/m²/hr). For UF membranes, typical values are 20–80 LMH depending on feed water quality. Clean surface water: 50–80 LMH. Secondary treated wastewater: 20–40 LMH. High-TSS industrial feeds: 15–25 LMH. Higher flux reduces membrane area but increases fouling and energy costs.
What is the temperature correction factor (TCF) for membranes?
TCF adjusts the design flux for water viscosity changes with temperature. The Metcalf & Eddy formula is: TCF = exp(0.0239 × (T – 20)), referenced to 20°C. At 15°C, TCF ≈ 0.888 (flux decreases ~11%). At 30°C, TCF ≈ 1.271 (flux increases ~27%). TCF is important for seasonal design in cold climates or for plants with significant temperature variation.
How many UF modules do I need for my plant?
Use this calculator: enter your net permeate flow, design flux, backwash factor, operating temperature, and module specifications. The calculator applies TCF, calculates gross flow, divides by corrected flux to get required area, then rounds up to whole modules and skids. For example: 50 m³/hr net flow, 40 LMH flux, 10% backwash, 25°C → approximately 1,414 m² required, 31 modules of 46 m² each, 4 skids of 8 modules.
Why is gross flow higher than net permeate flow?
UF membranes require periodic backwashing to remove accumulated foulants. During backwashing (typically every 20–60 minutes), clean permeate is pumped back through the membrane. This backwash water — 5–15% of gross production — is lost to drain or returned to the feed. The system must therefore produce more gross output than the net permeate requirement. Gross flow = Net flow ÷ (1 – backwash % / 100).
What is the difference between UF and MF membranes?
Microfiltration (MF) has larger pores (0.1–10 microns) and removes suspended solids, bacteria, and protozoa but not viruses. Ultrafiltration (UF) has smaller pores (0.01–0.1 microns) and additionally removes viruses, colloids, and high-molecular-weight organics. UF provides a stronger barrier for RO pre-treatment and is preferred in applications where virus removal is required. Both use similar hollow-fibre module designs and backwashing protocols.
Where is UF membrane technology used in India?
UF is deployed widely in India across: municipal drinking water treatment (Delhi, Bengaluru, Hyderabad), tertiary sewage treatment for water reuse in smart city projects, ZLD pre-treatment for RO in textile, pharma, and chemical ETPs, food & beverage and dairy effluent polishing, and seawater RO pre-treatment at coastal industrial plants. Key suppliers active in India include GE Suez ZeeWeed, DuPont Water Solutions, INGE (TORAY), and Pall Corporation.
Related Tools
RO Recovery Calculator
Calculate permeate, reject, TDS, and concentration factor for the RO stage downstream of UF.
ZLD Water Recovery Calculator
Estimate ZLD system cost, annual water savings, and payback for your zero liquid discharge project.
Secondary Clarifier Sizing
Size the secondary clarifier that produces the clarified effluent fed to UF in a full treatment train.
Design Your UF Membrane System
Spans Envirotech designs and commissions UF membrane systems for drinking water, tertiary wastewater polishing, and ZLD pre-treatment across India. Our engineers will validate your sizing, recommend modules, and prepare a detailed techno-commercial proposal.
Email: bd@spans.co.in